Liquid crystal display comprising first and second point light source assemblies wherein a first support substrate is larger than the second support substrate, and a first groove of a lower container is deeper than a second groove

ABSTRACT

A liquid crystal display includes a light guide plate guiding incident light, a first point light source assembly including first point light source elements providing the light to the light guide plate and a first support substrate having the first point light source elements, the first point light source assembly being disposed at one side of the light guide plate, a second point light source assembly including second point light source elements providing the light to the light guide plate and a second support substrate having the second point light source elements, the second point light source assembly being disposed at the other side of the light guide plate, a liquid crystal panel assembly disposed on the light guide plate and displaying image information, and a lower container accommodating the light guide plate, first and second point light source assemblies, and liquid crystal panel assembly, wherein the first support substrate is larger in area than the second support substrate.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent Application Nos.10-2006-0115165 and 10-2006-0123917 filed on Nov. 21, 2006 and Dec. 7,2006, respectively, the disclosures of which are incorporated herein byreference in their entireties.

BACKGROUND OF THE INVENTION

1. Technical Field

The present disclosure relates to a display, and more particularly to aliquid crystal display including a point light source assembly.

2. Discussion of the Related Art

Liquid crystal displays are widely used flat panel displays. A liquidcrystal display includes two substrates with electrodes and a liquidcrystal layer interposed between the substrates. The liquid crystaldisplay rearranges liquid crystal molecules in a liquid crystal layer byapplying a voltage to electrodes to control the amount of light passingthrough the liquid crystal layer.

Because these liquid crystal molecules display images by changing lighttransmittance according to the direction and magnitude of anelectromagnetic field, a liquid crystal display uses light fordisplaying images. Typical light sources used in liquid crystal displaysare, for example, a light emitting diode (LED), a cold cathodefluorescent lamp (CCFL), and a flat fluorescent lamp (FFL).

LEDs have a characteristic of low power consumption and high luminance.

The emitting efficiency of the LEDs changes according to the change of asurrounding temperature. The change of emitting efficiency of the LEDsresults in deterioration of display characteristics of liquid crystaldisplays. For example, the emitting efficiency of a red LED changessubstantially according to changes in a surrounding temperature, andcolor spots appear due to decreased color uniformity for each region.The decrease in color uniformity occurs because the surroundingtemperature is not uniform for each region of the liquid crystaldisplay.

SUMMARY OF THE INVENTION

According to an exemplary embodiment of the present invention, a liquidcrystal display includes a light guide plate guiding incident light, afirst point light source assembly which includes first point lightsource elements providing the light to the light guide plate and a firstsupport substrate having the first point light source elements and isdisposed at a side of the light guide plate, a second point light sourceassembly which includes second point light source elements providing thelight to the light guide plate and a second support substrate having thesecond point light source elements and is disposed at the other side ofthe light guide plate, a liquid crystal panel assembly disposed on thelight guide plate and displaying image information, and a lowercontainer accommodating the light guide plate, first and second pointlight source assemblies, and liquid crystal panel assembly. The firstsupport substrate can be larger than the second support substrate inarea.

According to an exemplary embodiment of the present invention, a liquidcrystal display includes a light guide plate guiding incident light, afirst point light source assembly which includes first point lightsource elements providing the light to the light guide plate and a firstsupport substrate equipped with the first point light source elementsand is disposed at a side of the light guide plate, a second point lightsource assembly which includes second point light source elementsproviding the light to the light guide plate and a second supportsubstrate having the second point light source elements and is disposedat the other side of the light guide plate, a liquid crystal panelassembly disposed on the light guide plate and displaying imageinformation, a lower container accommodating the light guide plate,first and second point light source assemblies, and liquid crystal panelassembly, and first and second heat conductive pads interposed betweenthe lower container and the first and second point light sourceassemblies, respectively. The first heat conductive pad can be largerthan the second heat conductive pad in area.

According to an exemplary embodiment of the invention, a liquid crystaldisplay includes a light guide plate guiding incident light, a pointlight source assembly including point light source elements providingthe light to the light guide plate and a support substrate having groupsof point light source element comprising at least one of the point lightsource elements, a lower container accommodating the light guide plateand point light source assembly, and a heat conductive pad interposedbetween the point light source assembly and the lower container. Theheat conductive pad can include unit regions having the groups of pointlight source elements, and the unit regions include a first unit regionand a second unit region wherein the first unit region and the secondunit region are different in size.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention can be understood in moredetail from the following descriptions taken in conjunction with theaccompanying drawings in which:

FIG. 1 is an exploded perspective view of a liquid crystal displayaccording to an exemplary embodiment of the present invention;

FIG. 2 is a graph showing a luminance of an emitting chip in relation toa surrounding temperature;

FIG. 3 is a partial perspective cut-away view illustrating a first pointlight source assembly and a lower container according to an exemplaryembodiment of the present invention;

FIG. 4 is a cross-sectional view of a liquid crystal display taken alongthe line IV-IV′ of FIG. 1;

FIG. 5A is an exploded perspective view showing a point light sourceassembly and a lower container accommodating the point light sourceassembly included in a liquid crystal display according to an exemplaryembodiment of the present invention;

FIG. 5B is a cross-sectional view of a point light source assembly and alower container taken along the line Vb-Vb′ of FIG. 5A;

FIG. 5C is a cross-sectional view of a point light source assembly and alower container taken along the line Vc-Vc′ of FIG. 5A;

FIG. 6A is an exploded perspective view showing a point light sourceassembly and a lower container accommodating the point light sourceassembly included in a liquid crystal display according to an exemplaryembodiment of the present invention;

FIG. 6B is a cross-sectional view of a point light source assembly and alower container taken along the line VIb-VIb′ of FIG. 6A;

FIG. 7A is an exploded perspective view of a point light source assemblyand a lower container accommodating the point light source assemblyincluded in a liquid crystal display according to an exemplaryembodiment of the present invention;

FIG. 7B is a cross-sectional view of a point light source assembly and alower container taken along the line VIIb-VIIb′ of FIG. 7A;

FIG. 8 is an exploded perspective view of a point light source assemblyand a lower container accommodating the point light source assemblyaccording to an exemplary embodiment of the present invention;

FIG. 9 is a first heat conductive pad according to an exemplaryembodiment of the present invention;

FIG. 10A is a perspective view of a point light source assembly includedin a liquid crystal display according to an exemplary embodiment of thepresent invention;

FIG. 10B is a plan view of a point light source assembly according to anexemplary embodiment of the present invention;

FIG. 11 is a diagram of a heat conductive pad of a point light sourceassembly according to an exemplary embodiment of the present invention;

FIG. 12A is an exploded perspective view of a backlight unit having apoint light source assembly according to an exemplary embodiment of thepresent invention;

FIG. 12B is a backlight unit according to an exemplary embodiment of thepresent invention;

FIG. 13 is a table illustrating heat dissipation effects of a pointlight source assembly;

FIG. 14A is a perspective view of a point light source assembly includedin a liquid crystal display according to an exemplary embodiment of thepresent invention; and

FIG. 14B is a plan view of a point light source assembly according to anexemplary embodiment of the present invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The invention is described more fully hereinafter with reference to theaccompanying drawings, in which exemplary embodiments of the inventionare shown. The invention may, however, be embodied in many differentforms and should not be construed as limited to the exemplaryembodiments set forth herein.

A liquid crystal display according to an exemplary embodiment of theinvention is described with reference to FIGS. 1 to 4.

FIG. 1 is an exploded perspective view of a liquid crystal displayaccording to an exemplary embodiment of the present invention.

Referring to FIG. 1, a liquid crystal display 100 according to anexemplary embodiment of the present invention includes a liquid crystalpanel assembly 130, a backlight unit 140, an upper container 110, and alower container 160.

The liquid crystal panel assembly 130 includes a liquid crystal panel136 including a lower display substrate 133, an upper display substrate134 and a liquid crystal layer (not shown) inserted between the displaysubstrates, a gate chip film package 131, a data chip film package 132,and a printed circuit board 135.

The liquid crystal panel 136 includes the lower display substrate 133that includes gate lines (not shown), data lines (not shown), a thinfilm transistor array, pixel electrodes and the upper display substrate134 that includes color filters, a black matrix, and a common electrodeand faces the lower display substrate 133. The color filters and commonelectrode may be formed on the lower display substrate 133. The liquidcrystal panel 136 displays image information.

The gate chip film package 131 is connected to each gate line (notshown) formed on the lower display substrate 133 and provides each gateline with gate driving signals. The data chip film package 132 isconnected to each data line (not shown) formed on the lower displaysubstrate 133 and provides each data line with data driving signals. Thegate chip film package 131 and data chip film package 132 include a TapeAutomated Bonding (TAB) tape with a semiconductor chip bonded with awiring pattern formed on a base film by Tape Automated Bonding (TAB).For example, for the gate and data chip film packages 131, 132, a tapecarrier package (TCP) or a chip on film (COF) can be used according toan exemplary embodiment of the present invention.

The printed circuit board 135 is mounted with a variety of drivingelements that process gate driving signals inputted into the gate chipfilm package 131 and data driving signals inputted into the data chipfilm package 132. The printed circuit board 135 is connected with theliquid crystal panel 136 and provides image information to the liquidcrystal panel 136.

The backlight unit 140 includes optical sheets 141, a light guide plate142, first and second point light source assemblies 145 a, 145 b, and areflecting sheet 146.

The light guide plate 142 guides light supplied from the first andsecond point light source assemblies 145 a, 145 b to the liquid crystalpanel 136. The light guide plate 142 comprises a plate of a transparentmaterial. For example, an acrylic resin, such as PolyMethyl MethAcrylate(PMMA), or polycarbonate can be used as the light guide plate 142. Whenincident light through a side of the light guide plate 142 reaches theupper or lower surface of the light guide plate 142 over the criticalangle of the light guide plate 142, the incident light is reflected fromthe surface of the light guide plate 142 and transmitted throughout theinside of the light guide plate 142 without leakage.

A diffusion pattern (not shown) is formed on at least one of the upperand lower surfaces of the light guide plate 142 to guide the lightinside the light guide plate 142 to travel to the liquid crystal panel136 disposed on the light guide plate 142. In an exemplary embodiment, adiffusion pattern may be formed on the lower surface of the light guideplate 142. That is, the light inside the light guide plate 142 isreflected from the diffusion pattern and travels outside through theupper surface of the light guide plate 142. The diffusion pattern formedon a surface of the light guide plate 142 may change in size and densityaccording to the distance from the first and second point light sourceassemblies 145 a, 145 b to maintain the light traveling outside throughthe entire surface of the light guide plate 142 uniform in luminance.For example, the larger the distance from the first and second pointlight source assemblies 145 a, 145 b, the larger the density or size ofthe diffusion pattern, so that the light traveling outside through theentire surface can be uniform.

The diffusion pattern may be formed by, for example, a silk screenprinting of ink. A diffusion pattern that has substantially the sameoperational effect may be formed by forming fine grooves or protrusionson the light guide plate 142.

The first and second point light source assemblies 145 a, 145 b aredisposed at both sides of the light guide plate 142. In an exemplaryembodiment, the light guide plate 142 can be formed, for example, in aflat plate shape with a substantially uniform thickness to uniformlytransmit light throughout the display.

The first point light source assembly 145 a supplies light to the liquidcrystal panel 136 that is a passive light emitting component. The firstpoint light source assembly 145 a includes a plurality of point lightsource elements 143 and a first support substrate 144 a having the pointlight source elements 143 disposed thereon. The second point lightsource assembly 145 b supplies light to the liquid crystal panel 136.The second point light source assembly 145 b includes a plurality ofpoint light source elements (not shown) and a second support substrate144 b having the point light source elements. The first point lightsource assembly 145 a is disposed on a first inside of the lowercontainer 160 that is close to the data chip film package 132. Thesecond point light source assembly 145 b is disposed on a second insidefacing the first inside of the lower container 160.

The point light source elements 143 are formed on sides of the first andsecond support substrates 144 a, 144 b at regular intervals by contactterminals. The first and second support substrates 144 a, 144 b may beformed into a long rectangular plate. For example, the first and secondsupport substrates 144 a, 144 b may be formed of a printed circuit board(PCB) or a flexible printed circuit board (FPC).

Each of the point light source elements 143 includes a light emittingelement that emits light, for example, directly. For example, the pointlight source element 143 may be an LED, an incandescent lamp, and awhite halogen lamp. Each of the point light source element 143 includesa frame (not shown) and red, green, and blue light emitting chipsdisposed inside the frame. White light is produced by mixing red, green,and blue light emitted from each light emitting chip.

FIG. 2 is a graph that shows a luminance of light emitting chips inrelation to a surrounding temperature. The relative luminance is basedon the luminance of light radiated from the light emitting chips at atemperature of about 25° C.

As shown in FIG. 2, relative luminance of a red light emitting chip Rrapidly changes with respect to temperature as compared with a greenlight emitting chip G and blue light emitting chip B. The point lightsource element 143 comprises the red, green, and blue light emittingchips R, G, B. When temperatures are different at each region where thepoint light source elements 143 are disposed, color scheme of red,green, and blue light radiated from each point light source element 143varies, which reduces color uniformity.

Referring to FIG. 1, the reflecting sheet 146 is disposed under thelight guide plate 142 and reflects light that travels down out of thelight guide plate 142 upwardly. The reflecting sheet 146 reduces loss oflight entering the liquid crystal panel 136 and improves coloruniformity of light passing through the exit surface of the light guideplate 142 by reflecting light, which is not reflected by the diffusionpattern on a side of the light guide plate 142, to the exit surface ofthe light guide plate 142.

For example, the reflecting sheet 146 may comprise polyethyleneterephthalate (PET) and a side of the reflecting sheet 146 may be coatedwith a diffusion layer that contains, for example, titanium dioxide. Astitanium dioxide is dried and fixed, light can be more uniformlydiffused by a white surface of frost formed by the titanium dioxide andpredetermined reflective effect is achieved.

The optical sheets 141, disposed on the upper surface of the light guideplate 142, diffuse and concentrate light transmitted from the lightguide plate 142. The optical sheets 141 include, for example, adiffusion sheet, a prism sheet, and a protection sheet. Disposed betweenthe light guide plate 142 and the prism sheet, the diffusion sheetprevents a partial concentration of light by distributing light from thelight guide plate 142. The prism sheet has an upper surface with apredetermined array of triangular prisms and may comprise, for example,two sheets. The prism arrays that cross with each other at apredetermined angle concentrate light diffused from the diffusion sheetperpendicularly to the liquid crystal panel 136. Accordingly, most lightpassing through the prism sheet perpendicularly travels and luminance isuniformly distributed on the protection sheet. The protection sheet,formed on the prism sheet, protects the surface of the prism sheet, anddiffuses light to uniformly distribute the light. Configuration of theoptical sheets 141 is not limited to the above and may be variouslymodified.

The liquid crystal panel 136 is formed on the protection sheet andplaced inside the lower container 160 together with the backlight unit140. The lower container 160 has sides formed along the edge of thebottom (see 164 in FIG. 3). The lower container 160 accommodates thebacklight unit 140 and the liquid crystal panel assembly 130 inside thesides. The lower container 160 prevents the backlight unit 140 with aplurality of sheets from being bent. The printed circuit board 135 ofthe liquid crystal panel assembly 130 is bent and placed onto theoutside of a side of the lower container 160, e.g., a rear side of thelower container 160. The lower container 160 may have a variety ofshapes, depending on, for example, the ways of disposing the backlightunit 140 or the liquid crystal panel assembly 130 into the lowercontainer 160.

The upper container 110 is combined with the lower container 160. Theupper container 110 covers the upper surface of the liquid crystal panelassembly 130 placed in the lower container 160. A window is formed onthe upper surface of the upper container 110 to expose the liquidcrystal panel assembly 130 to the outside.

The upper container 110 may be combined with the lower container 160 by,for example, hooks (not shown). In an exemplary embodiment, the hooksare formed on the outsides of the sides of the lower container 160 andcorresponding hook-inserting holes (not shown) are formed in the sidesof the upper container 110. Accordingly, when the upper container 110and the lower container 160 are combined by moving the upper container110 down over the lower container 160, the hooks of the lower container160 are inserted into the hook-inserting holes of the upper container110 and the upper container 110 is fastened with the lower container160. The upper container 110 and lower container 160 may be combined ina variety of ways.

FIG. 3 is a partial perspective cut-away view illustrating the firstpoint light source assembly 145 a and the lower container 160 accordingto an exemplary embodiment of the present invention. FIG. 4 is across-sectional view of a liquid crystal display taken along the lineIV-IV′ in FIG. 1.

Referring to FIGS. 3 and 4, as described above, the lower container 160has sides 162 formed along the edge of the bottom 164. A first groove166 a and a second groove 166 b are formed on the bottom 164 along twosides 162. The first and second point light source assemblies 145 a, 145b are inserted in the first groove 166 a and second groove 166 b,respectively. The first and second support substrates 144 a, 144 b areinserted into the first and second grooves 166 a, 166 b, respectively,close to the sides 162 of the lower container 160.

The first point light source assembly 145 a is disposed adjacent to theside 162 of the lower container 160, close to the data chip film package132, and the second point light source assembly 145 b is disposedadjacent to the opposite side to the first point light source assembly145 a. The region around the first point light source assembly 145 a ishigher in temperature than the region adjacent to the second point lightsource assembly 145 b due to the heat generated by a driving IC(integrated circuit) (IC) mounted in the data chip film package 132.Non-uniformity of temperature in the regions reduces color uniformity.

Heat generated from the point light elements 143 of the first and secondpoint light source assemblies 145 a, 145 b is conducted to the sides 162of the lower container 160 through the first and second supportsubstrates 144 a, 144 b and transmitted outside. To decrease thetemperature around the first point light source assembly 145 a, moreheat out of the first point light source assembly 145 a can bedissipated to the outside as compared with the second point light sourceassembly 145 b. In an exemplary embodiment, the area of the firstsupport substrate 144 a is larger than the second support substrate 144b. For example, the first and second support substrates 144 a, 144 b areformed into a long rectangular plate. In an exemplary embodiment, thesides of the first and second support substrates 144 a, 144 b can facethe sides 162 of the lower container 160, and the width W1 of the firstsupport substrate 144 a can be larger than the width W2 of the secondsupport substrate 144 b. For example, when the width W1 of the firstsupport substrate 144 a is 1.2 times larger than the width W2 of thesecond support substrate 144 b, the region around the first point lightsource assembly 145 a can decrease the temperature by about 2° C. toabout 5° C.

For the first point light source assembly 145 a disposed at therelatively high-temperature region, color uniformity can be improved byincreasing the area of the first support substrate 144 a facing the side162 of the lower container 160 while decreasing the surroundingtemperature.

Since the first support substrate 144 a is larger than the secondsupport substrate 144 b in area, the first groove 166 a may be formedwith a depth D1 which is larger than the second groove 166 b with adepth D2. Therefore, the point light elements 143 of the first andsecond point light source assemblies 145 a, 145 b are regularly locatedat predetermined positions, facing the light guide plate 142.

FIG. 5A is an exploded perspective view showing a point light sourceassembly and a lower container accommodating the point light sourceassembly included in a liquid crystal display according to an exemplaryembodiment of the present invention. FIG. 5B is a cross-sectional viewof a point light source assembly and a lower container taken along theline Vb-Vb′ in FIG. 5A. FIG. 5C is a cross-sectional view of a pointlight source assembly and a lower container taken along the line Vc-Vc′in FIG. 5A.

Referring to FIGS. 5A to 5C, a first point light source assembly 245 aincludes a plurality of point light elements 143 and a first supportsubstrate 244 a having the point light elements 143. A first groove 266a to receive the first point light source assembly 245 a and a secondgroove 166 b to receive the second point light source assembly 145 b areformed on the bottom of a lower container 260 along two sides 162.

Because the first point light source assembly 245 a is disposed close tothe data chip film package 132, the region around the first point lightsource assembly 245 a is higher in temperature than the region aroundthe second point light source assembly 145 b due to heat generated by adriving IC mounted in the data chip film package 132. The centralportion is higher in temperature than both sides in the first pointlight source assembly 245 a.

To decrease the temperature of the first point light source assembly 245a at a level approximate to the second point light source assembly 145b, the area of the first support substrate 244 a can be larger than thesecond support substrate 144 b. To decrease the temperature of thecentral portion at a level approximate to both side portions of thefirst point light source assembly 245 a, the central area can be formedlarger than the side portions of the first support substrate 244 a. Inan exemplary embodiment, the central width is larger than the side widthof the first support substrate 244 a. For example, the first supportsubstrate 244 a may be formed into a T-shape. When the central width isabout 1.1 to about 1.2 times larger than the side width of the firstsupport substrate 244 a, the central portion can decrease thetemperature by about 2° to about 5° C.

The side width of the first support substrate 244 a may be setsubstantially the same as or larger than the width of the second supportsubstrate 144 b.

Color uniformity of the LCD 100 can be improved by forming the centralwidth larger than the side width of the first support substrate 244 abecause the temperature of the central portion can be reduced.

Since the central width of the first support substrate is larger thanthe side width of the first support substrate 244 a, the correspondingcentral portion of the first groove 266 a can be formed deeper than thecorresponding side portions of the first groove 266 a.

FIG. 6A is an exploded perspective view showing a point light sourceassembly and a lower container accommodating the assembly included in aliquid crystal display according to an exemplary embodiment of thepresent invention. FIG. 6B is a cross-sectional view of a point lightsource assembly and lower container taken along the line VIb-VIb′ ofFIG. 6A.

Referring to FIGS. 6A and 6B, a first point light source assembly 345 aincludes a plurality of point light source elements 143 and a firstsupport substrate 344 a having the point light source elements 143. Afirst groove 366 a to receive the first point light source assembly 345a and a second groove (not shown) to receive the second point lightsource assembly 145 b are formed on the bottom of a lower container 360along two sides 162.

Because the first point light source assembly 345 a is disposed close tothe data chip film package 132, the region around the first point lightsource assembly 345 a is higher in temperature than the region aroundthe second point light source assembly 145 b due to heat generated by adriving IC mounted in the data chip film package 132. The centralportion of the first point light source assembly 345 a is higher intemperature than short-side portions of the first point light sourceassembly 345 a.

To decrease the temperature of the first point light source assembly 345a at a level approximate to the second point light source assembly 145b, the area of the first support substrate 344 a can be larger than thesecond support substrate 144 b. To decrease the temperature of thecentral portion of the first light source assembly 345 a to a levelapproximate to both side portions of the first point light sourceassembly 345 a, the central portion can be formed larger than the sideportions of the first support substrate 344 a. The central width of thefirst support substrate 344 a can be larger than the side width of thefirst support substrate 344 a. For example, the first support substrate344 a may be formed into an arch with a wide central portion.

Color uniformity of the LCD 100 can be improved by increasing thecentral width of the first support substrate 344 a than the side widthof the first support substrate 344 a.

Since the central width of the first support substrate 344 a is largerthan the side width of the first support substrate 344 a, the firstgroove 366 a can be formed in an arch with the central portion deeperthan the side portions to correspond to the shape of the first supportsubstrate 344 a.

FIG. 7A is an exploded perspective view of a point light source assemblyand a lower container accommodating the assembly included in a liquidcrystal display according to an exemplary embodiment of the presentinvention. FIG. 7B is a cross-sectional view of a point light sourceassembly and a lower container taken along the line VIIb-VIIb′ in FIG.7A.

Referring to FIGS. 7A and 7B, a first point light source assembly 445 aincludes a plurality of point light source elements 143 and a firstsupport substrate 444 a having the point light source elements 143thereon. A first groove 466 a to receive the first point light sourceassembly 445 a and a second groove 166 b to receive the second pointlight source assembly 145 b are formed on the bottom of a lowercontainer 460 along two sides 162.

Because the first point light source assembly 445 a is disposed close tothe data chip film package 132, the region around the first point lightsource assembly 445 a is higher in temperature than the region aroundthe second point light source assembly 145 b due to heat generated by adriving IC mounted in the data chip film package 132.

Heat generated from the point light source elements 143 in the firstpoint light source assembly 445 a is transmitted to the side 162 of thelower container 460 through the first support substrate 444 a and afirst heat conductive pad 400 a interposed between the first supportsubstrate 444 a and the side 162 of the lower container 460. Heatgenerated from the point light source elements 143 in the second pointlight source assembly 145 b is transmitted to the side 162 of the lowercontainer 460 through the second support substrate 144 b and a secondheat conductive pad 400 b interposed between the second supportsubstrate 144 b and side 162 of the lower container 460. Respectivelyinterposed between the first and second point light source assemblies445 a and 145 b and the side 162 of the lower container 460, the firstand second heat conductive pads 400 a, 400 b dissipate heat generatedfrom the first and second point light source assemblies 445 a and 145 bto the outside. The first and second heat conductive pads 400 a, 400 bmay be used to attach the first and second point light source assemblies445 a and 145 b to the sides of the lower container 460.

To decrease the temperature of the first point light source assembly 445a at a level approximate to the second point light source assembly 145b, the area of the first heat conductive pad 400 a can be larger thanthe second heat conductive pad 440 b. For example, when the first andsecond heat conductive pads 400 a, 400 b are formed into a longrectangular plate, the width of the first heat conductive pad 400 a canbe larger than the width of the second heat conductive pad 400 b. Forexample, when the width of the first heat conductive pad 400 a is 1.2times larger than the second heat conductive pad 400 b the first pointlight source assembly 445 a can decrease the temperature by about 2° C.to about 5° C.

Color uniformity of the LCD 100 can be improved by forming the width ofthe first heat conductive pad 400 larger than the second heat conductivepad 440 b.

In an exemplary embodiment, the first support substrate 444 a may have alarger area than the second support substrate 144 b to further decreasethe temperature around the first point light source assembly 445 a.

In an exemplary embodiment of the present invention, uniformity intemperature is achieved throughout the liquid crystal display 100 byforming the area of the first heat conductive pad 400 a larger than thesecond heat conductive pad 400 b. In an exemplary embodiment of thepresent invention, uniformity of temperature is achieved by using amaterial having a higher heat conductivity for the first heat conductivepad 400 a as compared with the second heat conductive pad 400 b.

FIG. 8 is an exploded perspective view of the point light sourceassembly and a lower container accommodating the assembly according toan exemplary embodiment of the present invention.

Because the first point light source assembly 445 a is disposed close tothe data chip film package 132, the region around the first point lightsource assembly 445 a is higher in temperature than the region aroundthe second point light source assembly 145 b due to heat generated by adriving IC mounted in the data chip film package 132. The centralportion is higher in temperature than short-side portions in the firstpoint light source assembly 445 a.

Heat generated from the point light source elements 143 in the firstpoint light source assembly 445 a is transmitted to the side 162 of thelower container 460 through the first support substrate 444 a and afirst heat conductive pad 500 a interposed between the first supportsubstrate 444 a and the side 162 of the lower container 460. Interposedbetween the first point light source assembly 445 a and the side 162 ofthe lower container 460, the first heat conductive pads 500 a dissipatesheat generated from the first point light source assembly 445 a to theoutside. The first heat conductive pad 500 a may be used to attach thefirst point light source assembly 445 a to the side of the lowercontainer 460.

To decrease the central temperature at a level approximate to the sideportions in the first point light source assembly 445 a, the centralarea is formed larger than the side areas in the first heat conductivepad 500 a. In an exemplary embodiment, the first heat conductive pad 500a has larger width at the central portion than the side portions. Forexample, the first heat conductive pad 500 a may have an H-shape. Forexample, as shown in FIG. 9, a first heat conductive pad 500 a′ may havea T-shape.

For the central portion of the first point light source assembly 445 adisposed at a relatively high-temperature region, color uniformity canbe improved by increasing the central width than the sides in the firstheat conductive pad 500 a with decrease in temperature.

In an exemplary embodiment, the color uniformity using the first heatconductive pad 500 a can be achieved by making the central portioncorresponding to the central portion of the first support substrate 444a of a material having a higher heat conductivity as compared with theside portions corresponding to the side portions of the first supportsubstrate 444 a.

FIG. 10A is a perspective view of a point light source assembly includedin a liquid crystal display according to an exemplary embodiment of theinvention. FIG. 10B is a plan view of the point light source assemblyaccording to an exemplary embodiment of the present invention. FIG. 11is a diagram of a heat conductive pad in a point light source assemblyaccording to an exemplary embodiment of the present invention.

Referring to FIGS. 10A and 10B, a point light source assembly 1400includes point light source components 1410, a support substrate 1430,and a heat conductive pad 1450. Each point light source element 1410includes a light emitting chip (not shown). The light emitting chip is aPN junction diode, in which when P- and N-type diodes are bonded and avoltage is applied to the diodes, and holes of the P-type semiconductorare concentrated on the intermediate layer of the N-type semiconductor.The electrons of the N-type semiconductor are concentrated on theintermediate layer that is the lowest part of a conduction band of theP-type semiconductor. The electrons drop on the holes of a valence band.When the electrons drop, energy corresponding to the difference inpotential levels of the conduction band and valence band, i.e. an energygap, is released into light. Alternatively, light emitting chip thatemits light in a variety of ways may be used. The light emitting chipcan emit light with a variety of wavelengths. To emit light with avariety of wavelengths, for example, it is possible to adjust content ofindium that is used as an active layer in nitride-based light emittingdiodes, to combine light emitting diodes that emit light havingdifferent wavelengths, or to combine a fluorescent body with a lightemitting chip that emits light in a predetermined range of wavelength,such as, for example, ultraviolet rays.

In an exemplary embodiment, the point light source elements 1410 areside view-typed light emitting diodes that emit light through the sides.The support substrate 1430 is formed with a circuit pattern to mount thepoint light source elements 1410. For example, the support substrate1430 may be any one of various printed circuit boards, such as, forexample, a Flexible PCB (FPCB), a common printed circuit board (e.g., arigid PCB), or a metal PCB.

The support substrate 1430 having the point light source elements 1410is disposed on the heat conductive pad 1450. The heat conductive pad1450 is interposed between the support substrate 1430 and the bottom ofa lower container (not shown) and dissipates heat generated from thepoint light source elements 1410 to the bottom of the lower container.The heat conductive pad 1450 may comprise a material having a good heatconductivity, such as, for example, metallic materials.

The entire region of the heat conductive pad 1450 is sectioned intoseveral unit regions where groups of the point light source elements (G₁to G₅) are disposed. That is, the heat conductive pad 1450 is sectionedinto a unit region A for a first point light source element group G₁, aunit region B for a second point light source element group G₂, a unitregion C for a third point light source element group G₃, a unit regionD for a fourth point light source element group G₄, and a unit region Efor a fifth point light source element group G₅. Each point light sourceelement group includes four point light source elements. That is, thefirst point light source element group G₁ includes a first point lightsource element 1410 _(1a) to a fourth point light source element 1410_(1d) and the other groups of point light source element havesubstantially the same configuration. In an exemplary embodiment of thepresent invention, four point light source elements are arranged in aline in each group of point light source element.

The heat conductive pad 1450 includes the central portion I with densepoint light source elements and edge portions II at both sides of thecentral portion I. The central portion includes the unit regions B, Cand D while the left and right edge portions II includes the unitregions A and E, respectively. In the heat conductive pad 1450, the unitregion pertaining to the edge portions II, i.e. the unit regions A or Eis formed smaller in area than any one of the unit regions pertaining tothe central portion I, i.e. the unit regions B, C and D. In an exemplaryembodiment, the unit regions A and E of the edge portions II are formedinto a trapezoid with the height Ly and the base L_(A) and L_(E),respectively. In an exemplary embodiment, the unit region B in thecentral portion I can be formed into a square or a rectangular shapewith the base L_(B) and the height L_(Y), where L_(A)=L_(B)=L_(E).

When the unit regions in the central portion I are larger in area thanthe unit regions in the edge portions II, the unit regions with densepoint light source elements 1410 is improved in dissipation efficiency,so that the heat conductive pad 1450 can be controlled to dissipate heatuniformly throughout the whole regions.

The heat conductive pad 1450 shown in FIG. 11 is sectioned into a unitregion A to a unit region E and formed into a substantially halfoctagon.

The upper side of the heat conductive pad 1450, i.e. the shorter side isabout 100 mm in length (L₂). The base opposite to the upper side, i.e.the longer side is about 265 mm in length (L₁). The first height H₁ isabout 15.75 mm, and the second height H₂ is about 30 mm. The dimensionof the heat conductive pad 1450 is a heat conductive pad according to anexemplary embodiment of the present invention and may be variouslychanged. For example, a ratio among each side can be when the shorterside of the heat conductive pad 1450 is 1 in length, the longer side maybe 2.6 to 2.8, the first height can be 0.1 to 0.2, and the second heightcan be 0.29 to 0.31.

FIG. 12A is an exploded perspective view of a backlight unit having apoint light source assembly according to an exemplary embodiment of thepresent invention. FIG. 12B is an exploded perspective view of abacklight unit according to an exemplary embodiment of the presentinvention.

Referring to FIGS. 12A and 12B, a backlight unit includes the lightguide plate 142, a point light source assembly 1400 that provides lightto the light guide plate 142, optical sheets 141 disposed on the uppersurface of the light guide plate 142, and a reflective sheet 146disposed under the light guide plate 142.

The point light source assembly 1400 includes point light sourceelements 1410 mounted on the support substrate 1430 and a heatconductive pad 1450 in which the unit regions pertaining to the centralportion are smaller in area than those pertaining to the edge portions.The point light source assembly 1400 is disposed at a side (see e.g.,FIG. 12A) or both sides (see e.g., FIG. 12B) of the light guide plate142 and used to provide light to the light guide plate 142. The lightguide plate 142 converts light with optical distribution of a pointlight source type that is generated from the point light source assembly1400 into light with optical distribution of a surface light sourcetype.

FIG. 13 shows a table for comparing heat dissipation of a point lightsource assembly of a relate art and a point light source assembly of anexemplary embodiment of the present invention. In FIG. 13, a point lightsource assembly that has a heat conductive pad in which the unit regionsin the central portion is the same as the unit regions in the edgeportion in area is selected for the related art, and a point lightsource assembly in which the unit regions in the central portion arelarger in area than the unit regions in the edge portions as describedabove is selected for an exemplary embodiment of the present invention.

According to the related art, the point light source elements at theleft edge were 44.4° C. in temperature, the point light source elementsat the right edge were 42.2° C., and the point light source elements atthe central portion were 47.4° C. Accordingly, it can be seen from thetable that the point light source elements at the central portion isabout 3 to about 4° C. higher than the edge portions. The differences intemperature are related to the differences in luminance of the pointlight source elements.

According to an exemplary embodiment of the present invention, the pointlight source elements at the left edge portion were 45.1° C. intemperature, the point light source elements at the right edge were45.9° C., and the point light source elements at the central portionwere 45.4° C. Accordingly, it can be seen from the table thatdifferences in temperature are not substantial in the point light sourceelements in an exemplary embodiment of the present invention. As aresult, luminance of the whole point light source elements on the heatconductive pad is almost uniformly distributed.

FIG. 14A is a perspective view of a point light source assembly includedin a liquid crystal display according to an exemplary embodiment of theinvention, and FIG. 14B is a plan view of a point light source assemblyaccording to an exemplary embodiment of the present invention.

The point light source assembly 1400 includes point light sourceelements 1410, a support substrate 1430, and a heat conductive pad 1460.

The entire region of the heat conductive pad 1460 is sectioned intoseveral unit regions where groups of point light source element (G₁ toG₅) are disposed. That is, the heat conductive pad 1460 is sectionedinto a unit region F for a first point light source element group G₁, aunit region G for a second point light source element group G₂, a unitregion H for a third point light source element group G₃, a unit regionI for a fourth point light source element group G₄, and a unit region Jfor a fifth point light source element group G₅. Each point light sourceelement group includes four point light source elements. That is, thefirst point light source element group G₁ includes a first point lightsource element 1410 _(1a) to a fourth point light source element 1410_(1d), and the other groups of point light source element havesubstantially the same configuration. In an exemplary embodiment of thepresent invention, four point light source elements are arranged in aline in each group of point light source element.

The heat conductive pad 1460 is divided into the central portion I withdense point light source elements and edge portions II at both sides ofthe central portion I. The central portion includes the unit regions G,H and I while the left and right edge portions II include the unitregions F and J, respectively. In the heat conductive pad 1460, the unitregion pertaining to the edge portions II, i.e. the unit regions F or Jis formed smaller in area than any one of the unit regions pertaining tothe central portion I, i.e. the unit regions G and I. In an exemplaryembodiment of the present invention, the unit regions F and J of theedge portions II are formed into a square or a rectangular shape withthe height L_(y2) and the base L_(F) and L_(J). The unit region G in thecentral portion I can be formed into a trapezoid with the base L_(G) andthe height L_(y1), where L_(F)=L_(J)=L_(G) and Ly₂<Ly₁. However, theshapes of the unit regions are not limited to the above and may bevariously modified.

According to an exemplary embodiment of the present invention, byincreasing a heat dissipating rate for point light source assemblies atrelatively high-temperature regions, color uniformity can be improvedthroughout a display.

Although the illustrative embodiments of the present invention have beendescribed herein with reference to the accompanying drawings, it is tobe understood that the present invention should not be limited to thoseprecise embodiments and that various other changes and modifications maybe affected herein by one of ordinary skill in the related art withoutdeparting from the scope or spirit of the invention. All such changesand modifications are intended to be included with the scope of theinvention as defined by the appended claims.

1. A liquid crystal display comprising: a light guide plate guidingincident light; a first point light source assembly including firstpoint light source elements providing the light to the light guide plateand a first support substrate having the first point light sourceelements, the first point light source assembly being disposed at oneside of the light guide plate; a second point light source assemblyincluding second point light source elements providing the light to thelight guide plate and a second support substrate having the second pointlight source elements, the second point light source assembly beingdisposed at the opposite side of the light guide plate; a liquid crystalpanel assembly disposed on the light guide plate and displaying imageinformation; and a lower container accommodating the light guide plate,first and second point light source assemblies, and liquid crystal panelassembly, wherein the first support substrate is larger in area than thesecond support substrate, wherein a number of the first point lightsource elements is same as a number of the second point light sourceelements, wherein the lower container comprises a bottom, a first sideand a second side substantially perpendicular to the bottom, a firstgroove disposed between the bottom and the first side, and a secondgroove disposed between the bottom and the second side, and the firstgroove is deeper than the second groove.
 2. The liquid crystal displayof claim 1, wherein the first support substrate is larger in width thanthe second support substrate.
 3. The liquid crystal display of claim 1,wherein a central portion is larger in width than edge portions in thefirst support substrate.
 4. The liquid crystal display of claim 1,wherein the first groove is deeper at a central portion than at edgeportions.
 5. The liquid crystal display of claim 1, wherein: the liquidcrystal panel assembly comprises a liquid crystal panel and a chip filmpackage connected to a side of the liquid crystal panel and providingdriving signals to the liquid crystal panel; and the first point lightsource assembly is disposed adjacent to the chip film package.
 6. Theliquid crystal display of claim 5, wherein the chip film package isconnected with data lines of the liquid crystal panel and provides datadriving signals to the liquid crystal panel.
 7. The liquid crystaldisplay of claim 1, further comprising: first and second heat conductivepads interposed between the lower container and the first and secondpoint light source assemblies, respectively.
 8. The liquid crystaldisplay of claim 7, wherein the first heat conductive pad is larger inarea than the second heat conductive pad.
 9. The liquid crystal displayof claim 8, wherein the first heat conductive pad is larger in widththan the second heat conductive pad.
 10. The liquid crystal display ofclaim 8, wherein the first heat conductive pad is larger in width at acentral portion than at edge portions.
 11. The liquid crystal display ofclaim 10, wherein the central portion comprises a material having a heatconductivity higher than a heat conductivity of the edge portions in thefirst heat conductive pad.
 12. The liquid crystal display of claim 1,wherein the one side and the opposite side of the light guide plate havea same length wherein the length is parallel with an arrangementdirection of the first point light source elements and the second pointlight source elements.